...
Buffer A: 11
Buffer C: 4
Worker X packing B: 3
Buffer B: 8
Worker Y packing C: 2
Buffer A: 12
Production line A suspended.
...

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <semaphore.h>
void *A(void *arg);
void *B(void *arg);
void *C(void *arg);

int main()
{
    int res, total = 0;
    pthread_t b_thread, e_thread, s_thread;
    void *thread_result;
    res = sem_init(&A, B, C 0, 0);
    if (res != 0) {
	perror("Semaphore initialization failed");
	exit(EXIT_FAILURE);
    }
//create the thread that prepares A
    res = pthread_create(&b_thread, A, NULL);
    if (res != 0) {
	perror("Thread creation failed");
	exit(EXIT_FAILURE);
    }
//create the thread that prepares B
    res = pthread_create(&s_thread, NULL, B, NULL);
    if (res != 0) {
	perror("Thread creation failed");
	exit(EXIT_FAILURE);
    }
//create the thread that prepares C
    res = pthread_create(&s_thread, NULL, C, NULL);
    if (res != 0) {
	perror("Thread creation failed");
	exit(EXIT_FAILURE);
    }
    and(getpid());
    while (total < 12) {
	sleep(rand() % 3 + 1);
	sem_post(&A);
	printf("A ready\n");
	total++;
    }
    printf("\nWaiting for thread to finish...\n");
    res = pthread_join(b_thread, &thread_result);
    if (res != 0) {
	perror("Thread join failed");
	exit(EXIT_FAILURE);
    }
    printf("Thread joined\n");
    res = pthread_join(s_thread, &thread_result);
    if (res != 0) {
	perror("Thread join failed");
	exit(EXIT_FAILURE);
    }
    printf("Thread joined\n");
    sem_destroy(&B);
    exit(EXIT_SUCCESS);
}
void *A(void *arg)
{
    int i;
    srand(time(NULL));
    for (i = 0; i < 7; i++) {
	sem_wait(&B);
	sleep(rand() % 4 + 1);
	printf("A prepared.\n");
    }
    pthread_exit(NULL);
}
void *B(void *arg)
{
    int i;
    srand(time(NULL));
    for (i = 0; i < 5; i++) {
	sem_wait(&A);
	sleep(rand() % 3 + 1);
	printf("B prepared.\n");
    }
    pthread_exit(NULL);
}
void *C(void *arg)
{
    int i;
    srand(time(NULL));
    for (i = 0; i < 5; i++) {
	sem_wait(&A);
	sleep(rand() % 3 + 1);
	printf("C prepared.\n");
    }
    pthread_exit(NULL);
}